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Thread: IPCC Fifth Assessment

  1. #1 IPCC Fifth Assessment 
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    Posting since we haven't discussed.
    First link is to the actual report (I'm just starting to read through it).
    If you don't have weeks, you might try the policy maker summary, which is the pdf document.

    My favorite chart so far is the simple one that shows radiative forcing changes in the lower atmosphere.

    IPCC - Intergovernmental Panel on Climate Change

    http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf



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    What is the NMVOC row? Are those anthropogenic volatile organics that break down into CO2, CH4 etc?


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    Speaking of radiative forcing charts, this one's always good for a laugh.





    So few laughs available around IPCC reports. Might as well take every one we can get.
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    Hello everyone,

    I'm hoping to discuss climate change without the use of the words believer and denier, as I feel that these terms are unscientific and detract from what could be a valuable and educational discussion.

    To Lynx_Fox and PhDemon: I noticed references to meteorology and climate science in your signatures, so I'm curious to know your thoughts on the implications of the above chart concerning an immediate threat to our civilization. Do you predict that the human race will be significantly impacted over the next 20 years? By this I mean mass preventable deaths, starvation, loss of inhabitable land, etc.
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    Honestly don't know. And your asking to go beyond the Earth sciences. It's more a question of how resilient our civilizations are--I say that because we do not have one..but many with overlap.

    Grave concerns.

    -Increasing cost to world economies to adjust to changes in agriculture and disasters such as severe droughts, flooding and sea level increases.

    -Many secondary effects of impoverished nations that turn into hot beds of terror with nothing to loose. This is already happening in places like Yemen and Somalia and in the next couple generations will effect Iraq, Iran and Syria as increasingly severe droughts and competition for water turn farmers into soldiers fighting over water.

    -Increasing ecological damage with many unknown impacts on humanity. One such example is the oceans' increasing acidity--there's already regional extinctions of shellfish near upwelling coast lines such as the US Pacific NorthWest.

    I think we'll see a pretty dramatic temperature increases in the next 20 years, as China, the number one CO2 emitting nation cleans up it's particulate pollution for its people's breathing health, much like Europe and American did during the 70's. China either goes nuke power or we're all going to be in a lot of trouble.

    I'm not an economist and really have no idea how fragile our entire international system of trade and commerce is the face of all these challenges. What we experience in the next 20 will likely be minor compared to the next 50.

    (it a lot like watching your neighbor continue to use his turkey deep fryer in his covered porch wondering when he's burn his house down and wouldn't really care if he his house was more than 20 feet from your own)
    --
    Reading the report for many of the details to the Earth's four spheres is challenging but predicting effects on our culture is far more difficult.
    Last edited by Lynx_Fox; October 13th, 2013 at 06:59 PM.
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  7. #6  
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    The latest paper on imminent impacts is this one. The projected timing of climate departure from recent variability : Nature : Nature Publishing Group

    a new index of the year when the projected mean climate of a given location moves to a state continuously outside the bounds of historical variability
    Being in Nature, it's behind a paywall, so you need other sources to get at the details.

    Urgent new time frame for climate change revealed by massive analysis
    Global warming

    Have a look at those. As for impacts within the next 20 years as against 20 years or more from now ... my own projection would be more of those fire followed by drought followed by flood type events we've been seeing in the USA. It really depends on the balance of el Nino and La Nina events in those 2 decades how many severe or prolonged droughts/ heatwaves/ extremely high temperatures we'll see in that time. Along with the consequences of reduced Arctic ice for longer and longer periods.

    The other important thing that's sort of there in temperature rises but not much discussed is the increased temperatures of overnight minimum temperatures. Not of much relevance to human comfort but absolutely vital to many crops. If this particular feature of increasing temperature continues faster than overall increases in average global temperatures, then large scale crop reductions or outright failures - mainly rice and corn/ maize - could become more common.
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    Thank you all for your informative answers. There does seem to be some uncertainty as to the severity and immediacy of the negative effects of climate change. Is it your observation that there is a consensus among scientists regarding anthropogenic global warming? Are those who speak out against the idea generally in the pay of fossil fuel producing corporations? Are there any reputable scientists among them? I hope these questions aren't too off-topic...
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    Quote Originally Posted by RobinM View Post
    Thank you all for your informative answers. There does seem to be some uncertainty as to the severity and immediacy of the negative effects of climate change.
    Not much. Most of the caveats in my responses were about dangers to our societies, not whether there would be negative severe effects caused by the global changes to climate. In other words is our modern connected international economy with still rapidly increasing technology enough to cope.

    Is it your observation that there is a consensus among scientists regarding anthropogenic global warming?
    Absolutely. Read the summary of the recent IPCC report...it is the single best source of scientific consensus on the topic.

    Are there any reputable scientists among them? I hope these questions aren't too off-topic...
    A few, mostly older chaps such as Dr. Lindzen of MIT, not sure if he ever got money from fossil fuel industry or just has a curmudgeonly stubborn/rebel streak (hehe) and William Gray, one of the original hurricane researchers.

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    Dr. Lindzen of MIT, not sure if he ever got money from fossil fuel industry or just has a curmudgeonly stubborn/rebel streak
    Can't find the exact quote right now, but lots of people say that Lindzen is extremely clever. The one that struck me went something like -

    Lindzen's used to being the smartest guy in the room, but he's only half as smart as he thinks he is.
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    Are those who speak out against the idea generally in the pay of fossil fuel producing corporations?
    There's a few who certainly are. Singer, Soon, Baliunas, anyone associated with the Heritage Foundation would fall into the funded-by-fossils category.

    But there are others. Some are driven by their religious views, Roy Spencer (Cornwell Alliance) would be the most eminent climate scientist here. Others are just a bit obsessive - Akasofu is a classic example of someone with a fixed idea ("cycles") and can't deal sensibly with the mainstream of the science, and he's far from the only one like that. There are only a few who manage to get anything published but it's normally in fringe or unrelated/ irrelevant/ vanity journals.

    And you also have to watch out for people claiming to be "climate scientists" who in reality have no relevant qualifications or research to their names. As well as a lot of people who make the mistake of thinking (most of them sincerely) that having any science degree at all gives them the necessary expertise to critique something they've never worked on. Considering the well-known - massive - clangers frequently dropped by Nobel Prize winners who venture out of their own field, ordinary scientists should have a bit more humility and willingness to listen to those with real expertise.
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  12. #11  
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    I'm having a difficult time finding a sea-level record that indicates accelerated rise. Would one of you provide a link? Thank you.
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    I've been looking for a couple of really good graphs that show the recent change in rate of SLR and can't find them for the life of me. This lot will have to do for the time being.

    1. Sea Level Rise: Faster than Projected | Open Mind


    2. This extract from How much will sea levels rise in the 21st Century? is reasonably good.

    In 2001, the IPCC Third Assessment Report (TAR) projected a sea level rise of 20 to 70 cm by 2100. In 2007, the IPCC Fourth Assessment Report (4AR) gave similar results, projecting sea level rise of 18 to 59 cm by 2100. How do the IPCC predictions compare to observations made since the two reports?


    Figure 1: Sea level change. Tide gauge data are indicated in red and satellite data in blue. The grey band shows the projections of the IPCC Third Assessment report (Allison et al 2009).

    Observed sea level rise is tracking at the upper range of model predictions. Why do climate models underestimate sea level rise? The main reason for the discrepancy is, no surprise, the effects of rapid flow ice changes. Ice loss from Greenland, Antarctica and glaciers are accelerating.


    3. This is a good article even though it's not directly related to the issue of recent acceleration in SLR. In the end our grandhildren's grandchildren won't much care how fast it happened for us, they'll just be looking for different places to live or to grow food.
    RealClimate: The inevitability of sea level rise




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    Even this one isn't the one I had in mind, but it's pretty good.

    The article is worth reading, as are the references.

    RealClimate: Sea-level rise: Where we stand at the start of 2013




    Fig. 3: Rate of global sea-level rise based on the data of Church & White (2006), and global mean temperature data of GISS, both smoothed. The satellite-derived rate of sea-level rise of 3.2 ± 0.5 mm/yr is also shown. The strong similarity of these two curves is at the core of the semi-empirical models of sea-level rise. Graph adapted from Rahmstorf (2007).


    Lots of good stuff at the Potsdam Institute site as well. This page in particular
    PIK Sea Level Pages
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    Thanks guys! Does the time period of 1880-1900 resemble 1980-2000 in this graph?

    File:Trends in global average absolute sea level, 1870-2008 (US EPA).png - Wikipedia, the free encyclopedia

    ..or am I reading it wrong?
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    This graph seems to indicate a drop in the rate of sea level rise from the late 40s to the late 70s. Do we know why that was?
    Quote Originally Posted by adelady View Post
    Even this one isn't the one I had in mind, but it's pretty good.

    The article is worth reading, as are the references.

    RealClimate: Sea-level rise: Where we stand at the start of 2013




    Fig. 3: Rate of global sea-level rise based on the data of Church & White (2006), and global mean temperature data of GISS, both smoothed. The satellite-derived rate of sea-level rise of 3.2 ± 0.5 mm/yr is also shown. The strong similarity of these two curves is at the core of the semi-empirical models of sea-level rise. Graph adapted from Rahmstorf (2007).


    Lots of good stuff at the Potsdam Institute site as well. This page in particular
    PIK Sea Level Pages
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  17. #16  
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    Quote Originally Posted by RobinM View Post
    Thanks guys! Does the time period of 1880-1900 resemble 1980-2000 in this graph?

    File:Trends in global average absolute sea level, 1870-2008 (US EPA).png - Wikipedia, the free encyclopedia

    ..or am I reading it wrong?
    Not sure what you mean by resemble but both are increasing the more recent at a greater rate.

    This graph seems to indicate a drop in the rate of sea level rise from the late 40s to the late 70s. Do we know why that was?

    The graph shows the reason, a slight drop in temperatures allowing more water to get locked up in land ice. Most hypothesis point to three causes for mid 20th century cooling: rapid industrialization and release of sun blocking aerosols (note the large effect of aerosols in the IPCC radiative chart earlier)--and subsequent clean up in the US and Europe starting about 1970; more aerosols from Mount Agung in 1963; and slight solar drop.
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    So the subsequent increase in sea level rise is at least partially attributed to the effects of clean air efforts in the 70s?
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  19. #18  
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    So the subsequent increase in sea level rise is at least partially attributed to the effects of clean air efforts in the 70s?
    Sorta but not really.

    We have no way of knowing what would have happened to the forests of Europe in particular if we'd allowed acid rain to eat them alive. The large scale death of trees and the exposure and degradation of millions of hectares of forest soils would have provided yet another boost to CO2 concentrations. Losses on swings and gains on roundabouts calculations might have been done but I've not heard of any.

    I've often wondered how much sooner people would have started making observations about the massive emissions from China if they'd had land / forest / lakes in the path of the plume rather than the empty expanses of the Pacific. I remember the shock of learning that fish were dying in Swedish lakes because of emissions blown across the Atlantic from American smokestacks. I can't have been the only one. It probably made getting clean air legislation through various parliaments a lot easier.
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    RobinM, The other aspect is even when they might appear to largely cancel each other out, such as during the mid-20th century, that is only for the global average temperatures. Each of the radiative forcing types have their own distribution. For example the long lived greenhouse gases such as CO2, are well mixed and tend to increase lower atmosphere temperatures at high latitudes more than equatorial latitudes. Aerosols act different. Some such as black soot on can increase temperature on snowy ground downwind of industry, others such as sulfur tend to reflect sunlight where it's of highest concentration downwind of industry/volcanic events. You add positive and negative feed backs from water vapor and other factors and it quickly adds up to the sort of complexity that make climate science particular fun to study.
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  21. #20  
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    One aspect of that 70s dip in temperatures was a decline in solar activity.

    Annual global temperature change (thin light red) with 11 year moving average of temperature (thick dark red). Temperature from NASA GISS. Annual Total Solar Irradiance (thin light blue) with 11 year moving average of TSI (thick dark blue). TSI from 1880 to 1978 from Krivova et al 2007 (data). TSI from 1979 to 2009 from PMOD (see thePMOD index page for data updates).


    And when you add in volcanic and other forcings you get this. The huge dips are the result of large volcanic eruptions.

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    This is fascinating stuff! It's no wonder climate science is so complex. Can anyone describe some of the mathematics used in this field? I've heard references to chaos theory. Also, what do you guys think of this paper:

    http://folk.uib.no/abo007/share/gree...ylek_box04.pdf

    Are these guys objective scientists?
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  23. #22  
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    Jason Box is one of the go-to people on the Greenland Ice Sheet.

    Here he is being interviewed. Jason Box: Weather Channel Interview on Ice and Sea Level Rise | Climate Denial Crock of the Week

    If you dig around at Climate Crocks you'll also find a few items on the Dark Snow project where the blogger accompanied the scientific team.

    If you're serious about the maths and physics of climate, you might give Science of Doom a go. Be prepared to take notes, revise your dusty textbooks and tolerate a reasonable amount of brain pain. Start at the roadmap page Roadmap | The Science of Doom and pick a series of posts that interests or puzzles you.

    Following Grant Foster's blog on statistical analysis is good value Double Standard | Open Mind even though it's often well above my pay grade. I just skip the bits where he gets into the nitty gritty of selecting or designing the testing / computing options and go to his results and conclusions.
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    This is a quote from the paper I posted:

    The Greenland surface air temperature trends over the past 50 years do not show
    persistent warming, in contrast to global average surface air temperatures. The
    Greenland coastal stations temperature trends over the second half of the past
    century generally exhibit a cooling tendency with superimposed decadal scale os-
    cillations related to the NAO. At the Greenland ice sheet summit, the temperature
    record shows a decrease in the summer average temperature at the rate of about
    2.2

    C/decade, suggesting that the Greenland ice sheet at high elevations does not
    follow the global warming trend either

    What do you guys think of this?
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  25. #24  
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    Haven't read it in detail, but some of it is probably just really bad timing and choice of time period in a wildly fluctuating location.

    Here's a collection of figures from several papers that go to about 2008 or so.

    Greenland
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    I'm a little confused here. The information in the link seems to indicate that CO2 doesn't factor into the the Greenland temperature cycle. Am I reading this wrong?

    The Greenland warming of 1920 to 1930 demonstrates that a high concentration of carbon dioxide and other greenhouse gases is not a necessary condition for period of warming to arise. The observed 1995-2005 temperature increase seems to be within a natural variability of Greenland climate. A general increase in solar activity [Scafetta and West, 2006] since 1990s can be a contributing factor as well as the sea surface temperature changes of tropical ocean [Hoerling et al., 2001]… To summarize, we find no direct evidence to support the claims that the Greenland ice sheet is melting due to increased temperature caused by increased atmospheric concentration of carbon dioxide. The rate of warming from 1995 to 2005 was in fact lower than the warming that occurred from 1920 to 1930.
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  27. #26  
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    What do you guys think of this?
    My first thought would be that an enormous amount of energy is going into the melting of the GIS and the Arctic sea ice. If it doesn't also warm the air above the ice, that's not really an issue. Atmospheric emperatures vary all over the world, as do temperature trends.

    Have a look at this overview of the whole of the Arctic.

    Scitation: The Arctic shifts to a new normal

    Global warming produces a larger effect in the Arctic than it does in midlatitudes, as shown in figure 3 and as predicted by Manabe and Stouffer.1 (Incidentally, Swedish scientist Svante Arrhenius was the first, in 1896, to quantify the contribution of CO2 to the greenhouse effect and to suggest greater warming in the Arctic than at lower latitudes.) Arctic air temperature increased in all seasons during the period 2000–09, with the greatest warming in autumn and winter.2 Mean annual temperature in the Arctic is now 1.5 °C higher than the 1971–2000 average; that’s more than double the warming at lower latitudes during the same period.
    (My emphasis.)
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    RobinM. Scafetta's cycles are a total dud.

    Here's an absolutely scathing demolition of a later paper. Mathturbation King | Open Mind

    (Unfortunately most of the archive at Tamino's has vanished so his similar discussion on Scafetts'a earlier work is mostly lost to us. Sometimes, if you know exactly what you want the wayback machine will get you there. But it's just a gamble.)

    This piece (the Intermediate level discussion) gives you a whole heap of more reliable references to analyses of those beloved "cycles".
    Sun & climate: moving in opposite directions
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    I wasn't familiar with Scafetta's cycles. The author of the article seems offended by Scafetta's sloppy science, and it is regrettable when scientists are less than thorough.

    Scafetta 2006 says "since 1975 global warming has occurred much faster than could be reasonably expected from the sun alone." from Sun & climate: moving in opposite directions

    He apparently came up with his cyclic hypothesis after this statement?

    Are you saying that Greenland is an anomaly, and we should focus on the Arctic?

    Do you and Lynx observe that humans as a species have become perceptive enough to build accurate climate models using computers?

    Sorry about all the questions! I'm just thrilled to discuss the climate without a lot of name-calling and unscientific behavior.
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    Progress in climate science has nothing to do with human species development of any kind. The biggest advantage that we have now in climate science is in massive computing power for running simulations and satellites for collecting data. But they're really not necessary to the understanding.

    Arrhenius's calculation of climate sensitivity to doubling of CO2 was done in 1896 with pen and ink - and the latest IPCC report includes much the same result. Hansen modelled climate impacts back in the 80s with computing power equivalent to a modern phone - and got it largely right.

    The basic physics of radiative gases - the greenhouse effect - was worked out by Tyndall back in the mid 19th century. The essential physics is really, really straightforward.

    Are you saying that Greenland is an anomaly, and we should focus on the Arctic?
    Nothing is "anomalous" unless we have presumed that global warming will always show up - every year, everywhere - in surface temperatures. That presumption is what leads some people astray. It's global warming, not always everywhere warming. (It's even possible to imagine a physically unlikely arrangement where all the warming, rather than 95% of it, goes into the oceans and melting the ice before affecting atmospheric temperatures. So there'd be rising sea levels and disappearing ice with no perceptible warming for those of us living in temperate and tropical regions unless our water supply relied on glaciers.)
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    Quote Originally Posted by adelady View Post
    Progress in climate science has nothing to do with human species development of any kind. The biggest advantage that we have now in climate science is in massive computing power for running simulations and satellites for collecting data. But they're really not necessary to the understanding.

    Arrhenius's calculation of climate sensitivity to doubling of CO2 was done in 1896 with pen and ink - and the latest IPCC report includes much the same result. Hansen modelled climate impacts back in the 80s with computing power equivalent to a modern phone - and got it largely right.

    The basic physics of radiative gases - the greenhouse effect - was worked out by Tyndall back in the mid 19th century. The essential physics is really, really straightforward.

    Are you saying that Greenland is an anomaly, and we should focus on the Arctic?
    Nothing is "anomalous" unless we have presumed that global warming will always show up - every year, everywhere - in surface temperatures. That presumption is what leads some people astray. It's global warming, not always everywhere warming. (It's even possible to imagine a physically unlikely arrangement where all the warming, rather than 95% of it, goes into the oceans and melting the ice before affecting atmospheric temperatures. So there'd be rising sea levels and disappearing ice with no perceptible warming for those of us living in temperate and tropical regions unless our water supply relied on glaciers.)


    I would imagine a land-based ice sheet like Greenland's wouldn't be reduced by rising ocean temperatures. It seems strange to me that Greenland's climate has been stable for 50 years, while the rest of the globe is undergoing profound warming. You also seem to be saying that climate predictions were correctly modeled in the 80's, and that the impact of CO2 in the atmosphere was estimated with a reasonable degree of accuracy in 1896? Please provide citations or links.

    Species development in terms of biological evolution was not what I meant. I was referring to technological capability, just to clarify.
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    I would imagine a land-based ice sheet like Greenland's wouldn't be reduced by rising ocean temperatures.
    You need to imagine a bit differently. The land-based ice sheets of Greenland and Antarctica are drained by glaciers. The ice-sheet accumulates ice from snowfall, the ice "flows" in accordance with gravity and the pressure of its own weight deforming and softening the ice. Geography of the underlying land concentrates some of that ice flow into glaciers. Those glaciers are, eventually, in contact with the ocean. When the water warms a bit, it is more capable of eating away at the undersides of the floating tongues of the glaciers. Those tongues are what slow the progress of the glaciers towards the ocean.

    When a weakened glacier breaks off more ice than usual, that is a bit less bulk and weight restraining the flow of the glacier. So the glacier speeds up. So more ice gets into contact with more water a bit faster. And once the process is releasing more ice than the ice-sheet gains each year from consolidating snowfall, the loss will continue and, as now, will accelerate if the previous gain/loss balance is not restored.

    As for Greenland not warming at the same pace as the rest of the world? I like the comparison in this extract with stuff we already know. That a drink full of ice cubes won't get warmer when it's warmed, the ice just melts faster. And there's a lot of ice to absorb the energy around Greenland.
    Interestingly enough, the models do not predict large trends in the vicinity of Southern Greenland over the last 100 or so years (the figure shows the ensemble mean results just from the GISS model, but others are similar). Mainly this is because these areas are relatively close to both open water and the ice sheet and that keeps temperatures pretty stable. Like a glass of water with ice cubes, any extra energy tends to go into melting rather than temperature changes. And in this region, changes in the AO pattern discussed above also appear to play some role. (It should also be noted that the trends in this region are not larger than the standard deviation, and so any one realisation is likely to have a lot of variability, as is seen in the observations).




    But if the models don’t show much change over the last 100 years, surely the predictions for the future indicate that this area will be hit hard? Again, no. Southern Greenland turns out to have one of the slowest rates of warming of any land area in any of the scenarios (the figure is the mean over all models for the SRES A1B scenario). To some extent, this is again due to the factors mentioned above, but additionally, the models predict that the North Atlantic as a whole will not warm as fast as the rest of globe

    As for models of the 80s. Hansen's is the most famous one. The only real error he made happened because he didn't have the kind of computing power we now have. Nowadays scientists let climate sensitivity emerge from running simulations, he actually had to put in some numbers. And he happened to use a number more appropriate to longer term outcomes than decadal projections.

    What do we learn from James Hansen's 1988 prediction?

    Had Hansen used a climate model with a climate sensitivity of approximate 3°C for 2xCO
    2(at least in the short-term, it's likely larger in the long-term due to slow-acting feedbacks), he would have projected the ensuing rate of global surface temperature change accurately. Not only that, but he projected the spatial distribution of the warming with a high level of accuracy. The take-home message should not be "Hansen was wrong therefore climate models and the anthropogenic global warming theory are wrong;" the correct conclusion is that Hansen's study is another piece of evidence that climate sensitivity is in the IPCC stated range of 2-4.5°C for 2xCO2.


    As for Arrhenius. Like so many others, his interest in climate began with explaining ice ages.

    Arrhenius figured out that an increase in the amount of carbon dioxide in the atmosphere would result in a certain amount of warming. In addition, it was already known via the Clausius-Clapeyron relation, that warmer air can hold more water vapour: the amount is about 7% more per degree Celsius of warming. And that additional water vapour would in turn cause further warming - this being a positive feedback, in which carbon dioxide acts as a direct regulator of temperature, and is then joined in that role by more water vapour as temperatures increase.


    Through further work Arrhenius determined that if you halved the amount of atmospheric carbon dioxide, the temperature of Europe could drop by as much as 4-5°C. But could such a change, big enough to cause an ice-age, occur? ...

    ... Side-tracking from the ice-age research, Arrhenius ran calculations to see what a doubling of carbon dioxide levels might do to temperatures. He came up with an answer of 5-6°C of warming as a globally-averaged figure.

    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
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    Thank you for expanding on your post. Here is an article that suggests the Greenland ice sheet is more stable than was previously thought:

    http://www.climatecentral.org/news/g...opposite-15500

    It also states that the Antarctic is less stable.

    I found this information on Milankovitch cycles to be very interesting: http://en.wikipedia.org/wiki/Milankovitch_cycleI assume you've read this? Such an amazing world we live on...
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  34. #33  
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    The idea of the Antarctic being less stable than previously thought is the sort of thing that makes some people lose a lot of sleep.

    As for Milankovitch cycles, I think they're fascinating. People tend to say that because of these you expect certain thing as certain intervals. But there are 3 cycles that enhance or detract from each other's effects as they coincide at peaks or at troughs. And if you look separately at the individual cycles rather than at the full combined graph, you can go badly wrong.
    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
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